title: A virtual frame system for stereotactic radiosurgery planning.
abstract: OBJECTIVE
  We describe a computerized (or virtual) model of a stereotactic head frame to enable planning prior to the day of radiosurgery. The location of the virtual frame acts as a guide to frame placement on the day of the procedure.
  
  
  METHODS
  The software consists of a triangular mesh representation of the essential frame hardware that can be overlaid with any MR scan of the patient and manipulated in three dimensions. The software calculates regions of the head that will actually be accessible for treatment, subject to the geometric constraints of the Leksell Gamma Knife hardware. DICOM-compliant MR images with virtual fiducial markers overlaid onto the image can then be generated for recognition by the treatment planning system.
  
  
  RESULTS
  Retrospective evaluation of the software on 24 previously treated patients shows a mean deviation of the position of the virtual frame from the actual frame position of 1.6 +/- 1.3 mm. Initial clinical use on five patients indicates an average discrepancy of the virtual frame location and the actual frame location of <1 mm. MR images with virtual fiducial markers can be imported into radiosurgical treatment planning software and used to generate an initial treatment plan.
  
  
  CONCLUSIONS
  The virtual frame provides a tool for prospective determination of lesion accessibility, optimization of the frame placement, and treatment planning before the day of the procedure. This promises to shorten overall treatment times, improve patient comfort, and reduce the need for repeat treatments due to suboptimally placed frames.
authors.affiliation: Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University, Baltimore, MD 21231, USA. eric.ford@jhmi.edu
authors.forename: Eric
authors.initials: E
authors.lastname: Ford
authors.forename: David
authors.initials: D
authors.lastname: Purger
authors.forename: Erik
authors.initials: E
authors.lastname: Tryggestad
authors.forename: Todd
authors.initials: T
authors.lastname: McNutt
authors.forename: John
authors.initials: J
authors.lastname: Christodouleas
authors.forename: Daniele
authors.initials: D
authors.lastname: Rigamonti
authors.forename: Ori
authors.initials: O
authors.lastname: Shokek
authors.forename: Sang
authors.initials: S
authors.lastname: Won
authors.forename: Jessica
authors.initials: J
authors.lastname: Zhou
authors.forename: Michael
authors.initials: M
authors.lastname: Lim
authors.forename: John
authors.initials: J
authors.lastname: Wong
authors.forename: Larry
authors.initials: L
authors.lastname: Kleinberg
mesh_terms: D001932:Brain Neoplasms / Q000473:pathology* / Q000601:surgery*; D003198:Computer Simulation; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008954:Models, Biological; D016634:Radiosurgery / Q000295:instrumentation / Q000379:methods*; D011880:Radiotherapy Planning, Computer-Assisted / Q000295:instrumentation / Q000379:methods*; D025321:Surgery, Computer-Assisted / Q000295:instrumentation / Q000379:methods*